84 lines
3.6 KiB
Markdown
84 lines
3.6 KiB
Markdown
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# steer
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Steer the brick in one direction using a turn ratio between two motors.
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```sig
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motors.largeAB.steer(0, 0)
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```
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A brick driving with two motors can steer itself by changing the speed of one motor compared to the speed of the other. To make a slow turn to the left, you might make the right motor run slightly faster than the left one. To make a fast, or sharp, turn to the right, the left motor could run at least twice as fast as the right one.
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The @boardname@ steers by using a percentage value of _follow_ for one of the motors. This means that the motor in the turn direction will rotate slower than the other. It is the _follower_ motor and the other motor is the _drive_ motor. The drive motor runs at a percentage of full speed set in **speed**. The follower motor runs at a percentage of speed of the drive motor. So, it runs at a percentage of a percentage of full speed.
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To make the turn happen you give a _turn ratio_ which is a percentage value of steer to the left or right. If you want to steer to the left at 30% of the of the drive motor speed, use the value of `-30` for **turnRatio**. Left turns use negative values and right turns use positive values. A really sharp turn to the right might use a turn ratio value of `80`.
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## Speed and distance
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The speed setting is a pecentage of the motor's full speed. Full speed is the speed that the motors run when the brick supplies maximum output voltage to the port.
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If you use just the **speed** number, the motors run continously and won't stop unless you tell them to. You can also give a value for a certain amount of distance you want the motors to rotate for. The **value** can be an amount of time, a turn angle in degrees, or a number of full rotations.
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If you decide to use a **value** of rotation distance, you need to choose a type of movement **unit**. Also, if you use a number of milliseconds as movement units, then you don't need to include the unit type. The description in [set speed](/reference/motors/motor/set-speed) shows how to use different movement units.
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## Parameters
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* **turnRatio**: a [number](/types/number) that is the percentage of speed of the drive motor. The follower motor runs at this speed. A negative number steers to the left and a positive number steers to the right. This is a number between `-100` and `100`.
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* **speed**: a [number](/types/number) that is the percentage of full speed. A negative value runs the motors in the reverse direction. This is the speed that the drive motor runs at.
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* **value**: the [number](/types/number) of movement units to rotate for. A value of `0` means run the motor continuously.
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* **unit**: the movement unit of rotation. This can be `milliseconds`, `seconds`, `degrees`, or `rotations`. If the number for **value** is `0`, this parameter isn't used.
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## ~hint
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** Reverse is negative speed**
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Steering the brick backwards (in reverse) is simple. Reverse is just a negative speed setting. To steer the brick to the left in reverse at 75% speed:
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```block
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motors.largeBC.steer(-15, -75)
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```
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## ~
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## Examples
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### Make a slight right
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Turn to the right with a turn ratio of 10%.
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```block
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motors.largeBC.steer(10, 55)
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```
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### Make a sharp left
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Turn sharply to the left.
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```block
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motors.largeBC.steer(-80, 40)
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```
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### Steer straight
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Use **steer** but go straight ahead.
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```block
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motors.largeBC.steer(0, 100)
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```
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### Sneaky snake
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Steer the brick in a snake pattern for a short time.
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```block
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for (let i = 0; i < 4; i++) {
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motors.largeBC.steer(30, 30)
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loops.pause(5000)
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motors.largeBC.steer(-30, 30)
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loops.pause(5000)
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}
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motors.stopAllMotors()
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```
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## See also
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[tank](/reference/motors/synced/tank), [set speed](/reference/motors/motor/set-speed)
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